The present invention relates to a manufacturing apparatus of a resin container to which a decorative design having a higher sense of togetherness can be applied by changing a thickness of a coating layer partially formed in a container body at a boundary portion between the coating layer and a part where the coating layer is not formed.
In recent years, a demand for resin containers has been increased. For example, various commercial products such as food products like beverage products or sanitary goods like a body soap or a shampoo are accommodated in resin containers and sold over counters. Under such circumstances, there are commercial products which have a tendency that conformations of their containers are similar because of characteristics of the commercial products, and it is often the case that similar commercial goods are accommodated in similar containers and sold.
On the other hand, general consumers consider a quality, a price and others of each commercial product when deciding purchase. Although it is a matter of course, an impression given by an appearance of a commercial good may have a great influence of a judgment upon purchase in some cases. In particular, when comparing commercial products which have almost no difference in quality, price and others, such a tendency becomes strong. Further, a container which is an appearance itself of a commercial product largely concerns formation of a commercial product image. In general, it can be said that earnings of a commercial product tend to increase when an excellent commercial product image is formed, but earnings of the commercial product tend to fail to rise when a bad commercial product image is formed. In this manner, an appearance of a commercial product, i.e., an impression which is given to consumers by a design of a container is very important in order to drive the consumers to buy.
Meanwhile, as a resin container in which the above-described commercial product is accommodated, one manufactured by a molding method called “blow molding” is generally used (see, e.g., a paragraph [0010] of Patent Reference 1: Japanese Patent Application Laid-open No. 2000-142662, a paragraph
of Patent Reference 2: Japanese Patent Application Laid-open No. 2000-238116 or the like). In blow molding, a molten material (a parison) extruded in a cylindrical shape from an extruder is held by a metal mold and air is blown into this material, thereby obtaining a hollow molded piece. Each of Patent Reference 1 and Patent Reference 2 discloses a multi-layer thin container which is provided with desired functional characteristics by adjusting an extruding quantity of a resin forming one layer when extruding a parison having a double-layered structure.
In such a resin container, a geometric design is applied and, on the other hand, a label sticker on which a commercial product name or the like is printed is put, or a film material such as a shrink label or a stretch label is attached so that commercial goods are discriminated. Further, there is appropriately performed direct printing on a container surface by appropriate printing means such as screen printing, uniform coloring of an entire container by adding a pigment or the like to a material resin forming the container, and others. These methods are generally utilized in order to apply a design using colors or colored patterns to containers.
In the method putting a sticker or attaching a film material, however, a sense of togetherness with a container is hard to be obtained, and the design is greatly limited. Furthermore, in such containers, labels must be separated at the time of discard, and hence it can be considered that containers with stickers or film materials are distantly respected by consumers. Moreover, in the method of performing direct printing on a container surface, for example, printing is difficult unless a relatively flat surface is provided, and hence there is a restriction in printing. Additionally, these methods are disadvantageous in terms of a manufacturing cost because they require a secondary process. On the other hand, in the method of coloring a container by adding a pigment or the like to a material resin, since molding and coloring can be simultaneously performed, this method is less disadvantageous in terms of a cost. However, a state of coloring is uniform in an entire container, and there is a drawback in which a change in colors cannot be expected.
As described above, in the conventional methods, various problems have been pointed out when applying a design using colors or colored patterns to containers. Although a container which appeals to consumers is demanded, an effective alternative idea has not been proposed yet. Even in Patent Reference 1 and Patent Reference 2 mentioned above, such design problems are not examined at all.
The present invention is proposed in order to solve the above-described problems of a prior art, and it is an object of the present invention to provide a manufacturing apparatus of a resin container, which can enhance the value of the container by, e.g., applying a decorative design having a high sense of togetherness to the container itself with a high degree of freedom.
The present invention is directed to a manufacturing apparatus of a resin container manufactured by blow molding a parison extruded from an extruder. The resin container comprises at least a container body and a coating layer which covers the whole or a part of the container body, the coating layer having a thickness reducing portion in which a thickness of the coating layer is successively reduced in a reduction rate of 0.1 to 1.5 μm/mm in a height direction of the container.
According to such a configuration, the value of the container can be enhanced by an excellent design effect or functional effect, thereby providing the resin container which greatly appeals to consumers.
Further, the resin container manufactured by the manufacturing apparatus according to the present invention can be configured in such a manner that the thickness reducing portion is formed in a range which occupies ¼ or more of a length of a container base portion in a height direction.
Adopting such a configuration can form a continuous gradation change in a wide range, thus improving design properties of the resin container.
Furthermore, the resin container manufactured by the manufacturing apparatus according to the present invention can be configured in such a manner that the coating layer disappears while reducing a thickness thereof, and a thickness reduction rate of the coating layer is 0.1 to 0.5 μm/mm at least in a range of 30 mm in the height direction immediately before a part at which the coating layer disappears.
Adopting such a configuration can provide directionality to a change in design or function realized by a change in thickness of the coating layer. In particular, when continuously changing a gradation to obtain a design effect, the thickness reduction rate in the range immediate before the coating layer disappearing part is set to the above-described range so that the change in gradation can be effectively prevented from being discontinued, thereby achieving the continuous and smooth change in gradation in the vicinity of the coating layer disappearing part.
Moreover, the resin container manufactured by the manufacturing apparatus according to the present invention is configured in such a manner that a color tone adjusting layer is provided on an outer surface side of the container body and the coating layer is formed on an outer surface side of the color tone adjusting layer.
According to such a configuration, forming the color tone adjusting layer which is used to adjust color tones of the container body and the coating layer can further improve design properties of the resin container.
Additionally, the resin container manufactured by the manufacturing apparatus according to the present invention can be configured in such a manner that a direction of a change in thickness of the coating layer along the height direction is opposite to a direction of a change in thickness of the color tone adjusting layer along the height direction at a part where the thickness reducing portion is formed.
According to such a configuration, it is possible to produce a continuous gradation change by combinations of colors of the container body, the coating layer and the color tone adjusting layer.
Further, when providing the above-described color tone adjusting layer, it is preferable for the resin container manufactured by the manufacturing apparatus according to the present invention that the coating layer and the color tone adjusting layer are formed of the same resin while considering printability at the time of printing a surface of the resin container. Furthermore, the coating layer and the color tone adjusting layer can be configured to contain a pearl pigment in order to give a pearly sense to the resin container.
Moreover, the resin container manufactured by the manufacturing apparatus according to the present invention may be configured to include an inner layer on an innermost surface of the container, or may be configured to include an outer layer on an outermost surface of the container. Additionally, it is preferable for the resin container manufactured by the manufacturing apparatus according to the present invention that MI of each of a base material resin forming the container body and a sub-material forming the coating layer is 0.1 to 30 g/10 min considering moldability.
Further, in the resin container manufactured by the manufacturing apparatus according to the present invention, a color which is similar to the color given to the container body but has a different color tone may be given to the coating layer, or a color whose hue is different from the color given to the container body may be given to the coating layer. According to such a configuration, a color itself of the resin container can be changed, thereby providing a decorative design having a high sense of togetherness. Demonstrating such a design effect can add a high value to the container, thus providing the resin container which further appeals to consumers.
Furthermore, the resin container manufactured by the manufacturing apparatus according to the present invention can be configured to contain an antibacterial agent in the coating layer.
According to such a configuration, since the coating layer which demonstrates an antibacterial function or a mildew resisting function is partially formed, an increase in cost can be suppressed, thus demonstrating a further effective antibacterial function or mildew resisting function with a small quantity of an antibacterial agent. Demonstrating such a functional effect can enhance the value of the container, thus providing the resin container which further appeals to consumers.
Moreover, a manufacturing method of a resin container by using a manufacturing apparatus according to the present invention is a method comprising: continuously supplying a base material resin forming a container body from a main extruder; discharging from a discharge portion provided in a die head a sub-material supplied from a sub-extruder so that the sub-material joins the base material resin; and extruding a parison from a slit portion opened on an end side of the die head; and blow-molding the parison, thereby forming a coating layer which covers the whole or a part of the container body by using the sub-material, wherein a thickness reducing portion in which a thickness is continuously reduced is formed in the coating layer while adjusting a resin pressure in a supply path of the sub-material fed from the sub-extruder by performing suck-back control which pulls back the sub-material from the discharge portion at an arbitrary timing when joining the sub-material with the base material resin.
By adopting such a method, a supply speed of the sub-material can be finely adjusted, a thickness of the coating layer can be continuously reduced at a small reduction rate, and a gradation change can be effectively prevented from being discontinued when producing the continuous gradation change in the thickness reducing portion to obtain a design effect in particular.
Additionally, in the manufacturing method of the resin container by using the manufacturing apparatus according to the present invention, it is preferable that the suck-back control is performed at least once before the resin pressure in the supply path of the sub-material is reduced to 70 to 15% of a maximum resin pressure when joining the sub-material with the base material resin, in order to effectively obtain an effect of the suck-back control, and it is also preferable that the suck-back control is performed before a reduction rate per unit time of the resin pressure in the supply path of the sub-material becomes 10% or below of a maximum reduction rate.
Further, in order to prevent a rate of change of the resin pressure after the suck-back control from being excessively increased, it is preferable for the reduction rate of the resin pressure in the supply path of the sub-material after the suck-back control to be five times or below the reduction rate before the suck-back control.
Furthermore, in the manufacturing method of a resin container by using a manufacturing apparatus according to the present invention, a direction of changing a thickness of the coating layer can be reversed by inverting a top side and a bottom side of a forming mold with respect to an extruding direction of a parison. Adopting such a method can express a symmetrical opposite change in color.
Moreover, in order to carry out the above-described manufacturing method, a manufacturing apparatus of a resin container according to the present invention is an apparatus comprising: a main extruder which supplies a base material resin; and a sub-extruder which supplies a sub-material, the sub-material supplied from the sub-extruder being discharged from a discharge portion provided in a die head so that the sub-material joins the base material resin continuously supplied from the main extruder, a parison being then extruded from a slit portion opened on an end side of the die head, the parison being subjected to blow molding, thereby forming a coating layer which covers the whole or a part of a container body formed of the base material resin by using the sub-material, wherein a suck-back mechanism which pulls back the sub-material from the discharge portion is provided between the sub-extruder and the die head, and
the discharge portion is provided in the vicinity of the slit portion in the die head. The manufacturing apparatus of a resin container according to the present invention can have a configuration in which the die head is provided with a flow path of the sub-material, the flow path being constituted of: an annular portion which is formed to relatively approximate the discharge portion as distanced from a side on which the sub-material is supplied; and a cone-shaped portion which is continuous with the discharge portion from the annular portion, and a second suck-back mechanism can be provided at a position close to the die head.
According to the present invention, the excellent design effect or functional effect enhances the value of the container, thus providing the resin container which greatly appeals to consumers.